Physical and psychological stress can alter the immune system in both humans and animals. Stress is also a known risk factor for some human diseases, such as autoimmune diseases and AIDS. Previous studies support the hypothesis that stressors modulate immune function through stress hormones such as endogenous opioids, other than exclusively glucocorticoids. However, the mechanisms by which stress affects the immune and neuroendocrine systems remain to be elucidated. During the last grant period, we discovered that restraint stress of mice induces immune suppression through the anti-apoptotic phosphatidylinositol 3-kinase (PI3K) and nuclear factor-kappaB (NF-kB) pathways. We have revealed that restraint stress of mice induces lymphocyte reduction in a pro-apoptotic p53-dependent manner. However, the precise mechanisms by which PI3K/NF-kB and p53 contribute to immune suppression are not known. The long-term goals of this revised application are to define the molecular mechanisms by which stress modulates immune suppression. Interestingly, we have recently identified a new endogenous inhibitor, [unreadable]-arrestin 2, a multifunctional adaptor and a signal transducer, which inhibit cell apoptosis through activation of anti-apoptotic PI3K and inhibition of pro-apoptotic p53 pathways in vitro. Moreover, we have found that mice with a deficiency in [unreadable]-arrestin 2 have dramatically enhanced sensitivity to restraint stress induced lymphocyte reduction. [unreadable]-arrestin 2 regulates the function of [unreadable] opioid receptor (MOR). In addition, MOR knockout mice have a significant inhibition of stress-induced reduction in lymphocytes. Our results showed that the specific MOR agonist induces T cell dysfunction through NF-kB and p38 mitogen-activated protein kinase (MAPK) pathways. Our overall hypothesis is that [unreadable]-arrestin 2 and MOR signaling pathways are critical to immune suppression. Moreover, we postulate that the mechanisms involve in the [unreadable]-arrestin 2 mediated PI3K and p53 pathways, and MOR-mediated NF-kB and p38 MAPK pathways. The first aim is to investigate the role of PI3K and p53 in [unreadable] -arrestin 2-mediated immune suppression. We will treat [unreadable] -arrestin 2 knockout mice and wild type mice with or without PI3K/p53 inhibitors, and then subject them to restraint stress. We will first examine the effects of [unreadable] -arrestin 2 on stress-induced immune suppression, and next define the role of [unreadable]-arrestin 2 mediated activation of PI3K and inhibition of p53 signaling in immune suppression. The second aim is to determine the contribution of NF-kB and p38 MAPK in MOR-mediated immune suppression. MOR knockout mice and wild type mice will be treated with or without NF-kB/p38 MAPK inhibitors and then subject them to physical restraint. We will first define the role of MOR in stress-induced immune suppression, and then examine the role of MOR-mediated NF-kB and p38 MAPK signaling in immune suppression. These studies should delineate the mechanisms underlying immune suppression induced by stress, providing the opportunity to develop novel strategies and therapeutics for immune suppression. [unreadable] PUBLIC HEALTH RELEVANCE: Stress, both physical and psychological, can have pronounced effects on the immune system. Historically this affect was attributed to the release of stress hormones although other factors appear to play an important role. Using a mouse model of restraint stress, we have determined some of the molecular mediators which may account for the connection between stress and the immune system. This research will examine the mechanisms whereby the immune system is influenced by stress with the hope of leading to the development of specific treatments or drugs which in turn may ameliorate this sometimes deleterious interaction. [unreadable] [unreadable] [unreadable]